The present invention relates to electrostatographic reproduction and more particularly to a transparent sheet material for making color transparencies by electrostatographic reproduction.
The art of electrostatographic copying is presently well developed and generally utilizes an electrostatic charge pattern on a photosensitive plate which is developed by contacting it with a particulate, electroscopic marking material known as toner. The toner is a pigment/resin mixture, which in the case of black and white reproduction, employs carbon black as the pigment. Recently, color electrostatographic copying has become commercially feasible. A commercial device for color copying is the Xerox 6500 Color Copier. This device employs three separate toners, pigmented yellow, cyan and magenta, and combinations thereof to provide multicolored copies.
The most common use of electrostatographic copiers involves transferring the toner image to plain paper. Fusing the toner into the paper provides a permanent copy. Another use relates to the substitution of a transparent sheet for the paper and transfer of the toner image thereto to provide imaged transparencies suitable for use in conjunction with overhead projectors. These transparent sheets are typically made from thin films of one or more organic resins. Polyester films are useful due to their physical properties but present the problem of poor toner adherence thereto. Typically a second resin film compatible with the toner is applied to one surface of the polyester base sheet to provide a two layered structure.
Two layered transparencies have been found to work well when each of the layers is selected of the proper material. However, two problems are sometimes encountered. The first is related to the electrostatic attraction between adjacent transparencies when they are stacked one on top of the other. This attraction complicates the process of automatically feeding the transparencies to provide a continuous process when it is desired to image several sheets. The other problem is related to toner disturbances which distort the image during transfer of the toner from the photosensitive plate to the blank transparency. This problem is especially acute when a multi-color transparency is being prepared.
It would be desirable and it is an object of the present invention to provide a novel transparency suitable for imaging by electrostatographic means.
Another object is to provide such a transparency which is especially suitable for multi-colored imaging.
An additional object is to provide such a transparency which can be readily fed from a stack thereof by automated means.